He has netted 15 goals and added seven assists in just 22 matches this campaign.
But the attacker was at the Bridge to see his former team-mate Nathaniel Chalobah, says the Daily Star.
Chalobah posted a message on Instagram saying: “Happy with our win and look at the smile on my face when I saw my bro @driesmertens after the game. Thanks for coming bro. Next stop Napoli to watch you. #NapoliMeetsLondon #alwaysagoodtime.”